Add write/readUTFArray interface to Portable Writer/Reader

[ihsandemir]

Portable writer/reader is missing the write and read UTF array which exis at Java API (https://github.com/hazelcast/hazelcast/blob/master/hazelcast/src/main/java/com/hazelcast/nio/serialization/PortableReader.java#L191 https://github.com/hazelcast/hazelcast/blob/master/hazelcast/src/main/java/com/hazelcast/nio/serialization/PortableWriter.java#L208)

[musaddiqrg]

This would be quite useful, was there a reason this was never done?

[ihsandemir]

@musaddiqrg I don't remember the reason why it can not be done. Especially, with the upcoming 4.0 release, we need to add this. I am reopening the issue.